Conventionally, a container made of synthetic resin having a handle is configured so that the handle is integrated with a recess formed in a side wall of a container body by engagement along a vertical direction of the container. In the case of manufacturing such a container, the handle is previously molded by injection molding etc. separately from the container body. Then, the molded handle is assembled to a mold and a preform is blow-molded inside the container mold. Thereby, the preform is caught by engaging parts formed to upper and lower portions of the handle, and the handle is integrated with the container body by engagement.
For example, the Patent Document 1 described below discloses a method for manufacturing a heat-resistant container with a handle in which blow molding is performed by setting a blow molding mold so that a trunk part central axis, which is at a lower side of a protrusion for handle attachment formed at an upper half part of the trunk part, is inclined to the side of the protrusion for handle attachment, and a wall surface around the protrusion for handle attachment is heat-treated.
Also, the Patent Document 2 described below discloses a plastic bottle with a handle in which the fitting strength of the handle is increased by forming the height of an upper extension part formed to an upper part of a holding part to be low, so that the handle is prevented from being detached from the bottle even when an impact is applied on the bottle by, for example, dropping the bottle on the floor.